One of the Kinahan cartel’s key lieutenants has become addicted to heroin and the crime gang now fears that the out-of-control gangster will become a major liability.

The gangland criminal, aged in his 30s, is now dependant on the highly addictive opiate and sources say he is “out of his mind on gear”.

As a result, he has become increasingly erratic over the last number of months.

This behaviour is causing huge paranoia within the feared gang, given his knowledge of its internal workings and his major involvement with many of its operations over a significant period of time.

There are fears within the Kinahan cartel that this individual could disclose key information to gardai investigating the gang, or rival members from the Hutch faction, as he is “liable to say anything to anyone”.

Pressure is now mounting on Daniel Kinahan to take out this individual after another criminal, who is facing serious charges, previously linked Kinahan to direct involvement in a murder plot.

The thug now addicted to heroin, who cannot be named for legal reasons, is a long-standing associate of the cartel and is suspected of involvement in at least one murder carried out on behalf of the dangerous mob.

He is a close business associate and personal friend of a number of high-ranking Kinahan members, and has spent most of his time between Dublin and mainland Europe.

“This lad would be seen as a tier one member of the cartel’s Dublin wing and he is now out of his mind almost every day on gear,” a source told the Herald.

“It now creates a huge problem for Daniel Kinahan and his gang, as this individual is a liability and could give information on the gang to rival gangs or gardai.

“This guy being on gear means that he is now liable to say anything to anyone. He knows where all the bodies are buried... literally.”

The thug has been involved in gangland activity over the last two decades and has been a primary target of national units, including the Drugs and Organised Crime Bureau (DOCB).

Almost 80 gardai are being added to the Garda national units, including the DOCB, in the fight against organised crime.

So far, 50 detective sergeants have been added to the Special Crime Operations (SCO) unit, with a further 30 detective gardai to join at the beginning of July.

They will be added to a number of the national units, including the DOCB, to help gardai combat organised crime.

Kinahan was the primary target in the Regency Hotel shooting last year when five armed men stormed the Dublin venue and opened fire.

He managed to escape the hotel through a back entrance as one of the gunmen shouted: “He’s not f**king in there. I can’t find him.”

The gang boss remains at the top of the Hutch hitlist.

Kinahan target James ‘Mago’ Gately – who cheated death when he was shot five times last month – has warned gardai that the deadly feud will not be over until Kinahan is killed.

“We will not rest until Daniel Kinahan is dead,” Gately warned detectives when they visited his Coolock home in the aftermath of the Regency Hotel attack.

“He caused all of this. It won’t end until he’s in his grave.”

After last month’s botched murder attempt by a professional cartel hit team at a busy petrol station, Gately (30) vowed Dublin’s gangland feud would continue.

Speaking from his hospital bed with a bullet lodged in his jaw, he told gardai: “I am not going down without a fight.”

Yesterday, the Herald revealed that members of Daniel Kinahan’s gang are so afraid of him that they refer to the crime boss only by a codename when discussing drug shipments and other crimes.

Criminals working for the cartel have started calling him ‘The Cap’ for fear of incriminating the mob leader.

The deadly Hutch/Kinahan feud has so far claimed 12 lives and gardai remain on high alert following the latest murder last month.

The number could have been higher if gardai had not disrupted more than 20 murder attempts in the last two years.

Gardai investigating the crime gangs involved in the ongoing feud say they have saved 25 lives.

Detectives from the DOCB have also seized €90m of drugs in the last two years, as well as 2,500 rounds of ammunition as they combat the “intensive” gang feud.